1. Field of the Invention
The present invention relates to a ceramic substrate (hereinafter abbreviated as a ceramic) which can be utilized as the electronic material such as dielectric porcelain substrate, etc., and a circuit substrate and an electronic circuit substrate by use of the ceramic and a method for preparing the ceramic.
2. Related Background Art
In the prior art, electronic circuit substrates have been constituted only of a conductive circuit, of a conductive circuit and resistance, or of a conductive circuit, resistance and a limited range of capacitor, and other functional portions are mounted separately as elements on the substrate.
For example, in a porcelain substrate of the prior art, the substrate was primarily one having conductors and resistors built therein, with the capacitors being mounted by soldering as the chip component, etc. For this reason, miniaturization of electronic circuit has been limited. FIG. 1 shows an example of the prior art. 111 is a porcelain substrate, 112 a conductor circuit, 113 a resistor and 114 a chip capacitor.
In recent years, attempts have been made to build in a plurality of capacitors within the substrate by varying the dielectric constants within the same porcelain substrate. However, it has been very difficult to form different dielectric portions within the same substrate, and a substrate having a plurality of capacitors built therein has not be realized or practically applied under the present invention, as is evident in view of, for example, cumbersomeness in the case of preparing a laminated ceramic capacitor. Also, it has been an important technical task to make the high dielectric constant portions sufficiently separated from each other as element functional portions without influence from each other within the limited structural space.
Further, the problems of separated built-in functional portions involved about such electronic component or circuit substrate are not limited to dielectric porcelain but they are universally exhibited when two or more same or different functional portions are to be formed within a ceramic.